Traditional voice telephony products are band-limited to 4 kHz bandwidth with 8 kHz sampling. These products include the telephone, data modems, and fax machines. Newer products aiming to achieve higher voice quality have doubled the sampling rate to 16 kHz to encompass a larger 8 kHz bandwidth, which is also known as “wideband” capable. The software implications of doubling the sampling rate are significant. Doubling the sampling rate not only requires doubling the processing cycles, but nearly doubling the memory used to store the data. In addition, software supporting wideband capabilities must not preclude support for legacy 4 kHz band-limited functionality.
Doubling memory and processor cycles requirements is expensive because the memory and processing power footprints of digital signal processors (DSPs) are generally small. Implementing wideband support thus requires creativeness to optimize both memory and cycles.
Additionally, much of the software providing various functions and services, such as echo cancellation, dual-tone multi-frequency (DTMF) detection and generation, and call discrimination (between voice and facsimile transmission, for example), are written for only narrowband signals. Either new software must be written for wideband signals, or the wideband signal must be down-sampled. Where the software is modified, the software should also be capable of integration with preexisting narrowband devices. Providing software for operation with both narrowband and wideband devices is complex and costly.
Accordingly, there is a need for splitting functionality for splitting a wideband data stream into a low-band data stream and a high-band data stream, as well as combining functionality for combining a low-band data stream with a high-band data stream to produce a wideband data stream.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.